1. Field
Embodiments of the present invention relate to apparatus and methods of providing a buffer for a human joint so as to prevent painful bone on bone contact. More particularly, embodiments of the present invention present a buffer for insertion between the femur and tibia in the human knee, so as to protect worn or damaged articular cartilage or exposed bone and to allow the articular surfaces remaining on the femur and tibia to continue to move against each other less painfully.
2. Description of the Related Art
The human knee joint is one of the most complex joints of the body and is also highly susceptible to damage because it is a weight bearing joint. The knee joint itself is comprised of the femur (thigh bone), the tibia (shin bone), the patella (kneecap), articular cartilage, and menisci, which are a type of crescent-shaped cartilage that lies between the femur and tibia. The menisci are located in the medial and lateral articulations of the knee and sometimes act as shock-absorbing pads. The knee is also compromised of tissues that are muscle, ligament, the lining tissue (synovium), and the synovial fluid which is secreted by the synovium.
The ends of the femur and tibia are coated with articular cartilage, which is smooth and hard, so as to provide the femur, tibia, and patella with a slick surface during normal movement. The articular cartilage has a very low coefficient of friction and can also receive large compressive loads, which makes it vital to ensure ease of movement of the knee joint and prevent bone on bone contact between the femur and tibia. Normal articular cartilage is about 50 times slicker than ice.
Over time, the articular cartilage on the femur and tibia, and in any other human joint, wears and degenerates, such that it thins or in some joints is completely lost. Upon wear of the articular cartilage, the slick, low friction surfaces from the cartilage are lost, and the ends of the femur and tibia banes are exposed. Without any protecting articular cartilage, the femur and tibia contact each. This bone on bone contact is painful, and is often the end result of osteoarthritis. Additionally, bones can also become hard and sclerotic over time with associated loss of articular cartilage, which can further increases the pain.
Many methods have been developed to either replace worn cartilage or otherwise minimize the pain associated with the loss of the articular cartilage. The methods have all had varying degrees of success but are often accompanied by very extensive and invasive surgery. All invasive methods are costly, often requiring implanting nonbiologic parts within the knee, or, in some instances, human cadaver parts. These methods of treatment also require lengthy rehabilitation, which often times leaves the patient in considerable pain.
One method of treatment that has been used is implantation of cadaver menisci. This method has had only limited success and multiple failures. A second method is chondroplasty, or removal of and thinning out the existing damaged cartilage. This method is used to smooth the cartilage to reduce the friction between the femur and tibia, and remove the flaps of cartilage that have delaminated from the bone. The success of this procedure is limited by the amount of cartilage remaining, and doctors guard against removal of too much of the articular cartilage so as to prevent exposure of the subchondral bone. For older patients or patients with traumatic arthritis of their knees, chondroplasty has only limited application because of the lack of healthy articular cartilage.
If the articular cartilage loss is small, an osteochondral autograft transplant (known as an OATS procedure) can be performed. The OATS procedure requires removing a dowel shaped portion of bone and replacing it with a commensurate dowel shaped portion of articular cartilage from another area of the knee, another joint, or even a cadaver. The OATS procedure is relatively invasive, has a fairly lengthy rehabilitation time, and has also only had limited success.
An even further alternative to repairing articular cartilage damage is growing the patient's own cartilage in tissue cultures and placing the newly grown cartilage in the areas of cartilage loss. This is an expensive and often unsuccessful method of treatment.
In the most extreme of cases of arthritis, the knee joint may be artificially resurfaced or even replaced. In artificial joint replacement, the ends of the femur and tibia are capped with plastic or metal pieces that are cemented to the ends of the bone. Alternatively, the ends of the femur and tibia can be replaced with a biologic ingrowth coating of the metal used, which removes the need for the cement. This procedure is presently the standard approach to treating severe osteoarthritis of the knee; however, the risks from this procedure are numerous, and this is particularly unfortunate for patients who can ill afford a major complication from this extensive surgery. In places where these artificial joints have been inserted, wear eventually occurs in the polyethylene surface between the metal caps, which can lead to bone destruction just from the particles of the polyethylene. Moreover, this procedure is not only quite invasive but requires a lengthy rehabilitation time. Thus, for these reasons, many doctors delay as long as possible this invasive procedure in many patients.
An even further method of treatment is arthrosporic debridement, which is much less invasive but almost always unsuccessful in limiting the pain from the damaged joint surface, unless most of the pain is from a torn cartilage or loose body in the joint that can be removed arthroscopically.
The problems associated with each of the above procedures are highly dependant on the age and medical condition of the patient. For older patients, their ability and desire to engage in an invasive procedure that requires lengthy rehabilitation is often limited. Moreover, for older patients who are not necessarily engaging in many activities or who do not require a long-term solution to adjust their pain and discomfort, having an invasive, complicated procedure performed is not ideal.
Accordingly, there is a need for a less risky and improved apparatus and method for alleviating and addressing pain resulting from a loss of articular cartilage. There is a need for a new apparatus and method of treatment of lost cartilage that extends beyond attempting to fix or replace damaged cartilage, but instead provides an apparatus and method of treatment that is minimally invasive, relatively inexpensive, requires relatively short rehabilitation time, and is suitable for older patients. This invention solves many of the above-described problems and provides a distinct advantage in the art of medical treatment for prevention of bone on bone contact due to the loss of articular cartilage. More particularly this invention provides a new apparatus and method of treatment to address the pain and discomfort associated with the loss of articular cartilage by interposing a thin but slick barrier between the tibia and femur. This invention provides a buffer between the femur and tibia in the human knee that does not require suturing or other permanent securement to muscles, ligaments, or tendons in the knee.